To answer my own question here's the first review. Bill Hunt over at The Digital Bits has seen season 2. In a nutshell, season 2 looks and sounds hardly any better than season 1 but the extra's are abundant and lengthy. The cast reunion is 95 minutes long!

I think things look better. The live action is roughly the same, but what I've watched so far of the episodes, the CGI doesn't look as low resolution in S2 even though it technically was also mostly rendered at 480p.